The present disclosure relates generally to the field of batteries, battery modules, and battery housings. More specifically, the present disclosure relates to battery housings for battery modules that may be used in vehicular contexts, as well as other energy storage/expending applications.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
A vehicle that uses one or more battery systems for providing all or a portion of the motive power for the vehicle can be referred to as an xEV, where the term “xEV” is defined herein to include all of the following vehicles, or any variations or combinations thereof, that use electric power for all or a portion of their vehicular motive force. As will be appreciated by those skilled in the art, hybrid electric vehicles (HEVs) combine an internal combustion engine propulsion system and a battery-powered electric propulsion system, such as 48 volt (V) or 130V systems. The term HEV may include any variation of a hybrid electric vehicle. For example, full hybrid systems (FHEVs) may provide motive and other electrical power to the vehicle using one or more electric motors, using only an internal combustion engine, or using both. In contrast, mild hybrid systems (MHEVs) disable the internal combustion engine when the vehicle is idling and utilize a battery system to continue powering the air conditioning unit, radio, or other electronics, as well as to restart the engine when propulsion is desired. The mild hybrid system may also apply some level of power assist, during acceleration for example, to supplement the internal combustion engine. Mild hybrids are typically 96V to 130V and recover braking energy through a belt or crank integrated starter generator. Further, a micro-hybrid electric vehicle (mHEV) also uses a “Stop-Start” system similar to the mild hybrids, but the micro-hybrid systems of a mHEV may or may not supply power assist to the internal combustion engine and operates at a voltage below 60V. For the purposes of the present discussion, it should be noted that mHEVs typically do not technically use electric power provided directly to the crankshaft or transmission for any portion of the motive force of the vehicle, but an mHEV may still be considered as an xEV since it does use electric power to supplement a vehicle's power needs when the vehicle is idling with internal combustion engine disabled and recovers braking energy through an integrated starter generator. In addition, a plug-in electric vehicle (PEV) is any vehicle that can be charged from an external source of electricity, such as wall sockets, and the energy stored in the rechargeable battery packs drives or contributes to drive the wheels. PEVs are a subcategory of electric vehicles that include all-electric or battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicle conversions of hybrid electric vehicles and conventional internal combustion engine vehicles.
xEVs as described above may provide a number of advantages as compared to more traditional gas-powered vehicles using only internal combustion engines and traditional electrical systems, which are typically 12V systems powered by a lead acid battery. For example, xEVs may produce fewer undesirable emission products and may exhibit greater fuel efficiency as compared to traditional internal combustion vehicles and, in some cases, such xEVs may eliminate the use of gasoline entirely, as is the case of certain types of PHEVs.
As xEV technology continues to evolve, there is a need to provide improved power sources (e.g., battery systems or modules) for such vehicles. For example, it is desirable to increase the distance that such vehicles may travel without the need to recharge the batteries. Additionally, it may also be desirable to improve the performance and reliability, and reduce the maintenance associated with such batteries.
One example of a battery module useful for the applications described above is one that includes multiple lithium ion electrochemical cells and other features for managing the operation of the cells under various conditions. Indeed, the ability of lithium ion electrochemical cells to be charged faster and in a more reproducible manner than other battery technologies (e.g., lead-acid electrochemical cells, nickel-cadmium electrochemical cells) makes them particularly suited to address various power requirements of the applications noted above. In this regard, many xEV applications include battery modules based on lithium ion technology, either alone or in combinations with other energy storage and supply technologies (e.g., ultracapacitors, lead-acid batteries).
The lithium ion electrochemical cells generally include non-aqueous liquids (e.g., aprotic organic solvents) as their electrolyte liquids, for example due to the incompatibility of lithium metal with water. In this regard, each electrochemical cell will generally include its own casing used to contain its specific components (e.g., electrodes, electrolyte fluids). Also, the lithium ion electrochemical cells and, in some instances, a housing of the battery modules containing these cells, may be hermetically sealed to limit exposure of the electrochemical cells and their internal components to moisture.
During operation (e.g., charging and discharging), the lithium ion electrochemical cells may become heated as a result of various electrochemical and thermodynamic processes occurring within the cells. This heat may cause the electrolyte liquids, among other things, to expand and in some situations volatilize, which in turn raises the internal pressure of the electrochemical cell and causes the individual casing of the electrochemical cells to expand. Further, as the lithium ion electrochemical cells experience an increase in internal pressure, they may begin to vent certain gases. For example, vented gases may include, but are not limited to, volatilized electrolyte.
For this reason, lithium ion electrochemical cells may be designed to withstand a certain amount of expansion, and may also include various interconnects or other features for venting gases into the battery module. Despite these approaches, in some instances, the degree of heating, or some other force placed upon lithium ion electrochemical cells, may be sufficient to cause one or more of the lithium ion electrochemical cells to vent a relatively large volume of gases into the housing of the battery module. To prevent rupture of the housing of the battery module, these gases may need to be vented as well.
Battery modules, therefore, may include a vent that is either connected to a vent tube in a vehicle or is sealed with a valve, or both, which enables the release of these gases from the battery module and into the vent tube of the vehicle or the ambient environment. However, it is presently recognized that the vents associated with such modules may be subject to further improvement, for example if the housing of a battery module were to enable directional venting of the gases, and/or multiple venting operations.